The embodiments described herein relate generally to endoscopic scanning methods and apparatus and, more particularly, to a photoacoustic endoscope that enables both photoacoustic imaging and ultrasonic imaging through the use of a rotatable reflector, such as a prism or a mirror.
Photoacoustic microscopy or computed tomography is an emerging imaging modality that has much potential for in vivo structural and functional imaging of biological tissues. It can produce spectroscopic optical absorption-based contrast images in optically scattering media such as human tissue while maintaining high spatial resolution (up to approximately 10 μm). In addition to the intrinsic contrast, by employing other biocompatible molecular contrast agents, such as organic dyes, quantum dots, or nano-particles, lesions can be profiled with molecular contrasts at high resolution.
Photoacoustic waves are generated by the instant thermal stress of biological tissue induced by an external energy supply, typically through a laser pulse although radiofrequency or microwave pulses may also be used. Even with weak light illumination, less than the ANSI safety limit (20 mJ/cm2 per laser pulse), detectable acoustic waves can be generated by the photoacoustic phenomenon, and cross-sectional or volumetric images of internal structures can be reconstructed by moving the illumination and detection points over the region of interest. To acquire the photoacoustic signal, typically a light delivering unit, a signal detection unit including an ultrasonic transducer, and a mechanical scanning unit are employed.